What is the speed that dust is ejected from the nucleus of a comet? (into the coma)
An expert replied to me "0.6 km/s", but I would very much prefer if I would measure it!

Pointing at the comet nucleus, I should see some solar spectrum reflected on the dust. Dust would be thrown out in every direction, so Doppler-Fizeau effect should "widen" any absorption lines from the solar spectra.

Am I correct in thinking that at a phase angle of 35º, the widest an absorption line could be widened is 2*cos^2(35º) * 2*(0,6/c)*wavelength ? So for H-alpha, this is still 1/3 of the resolution of my Lhires III

Comet C/2014 Q2 (Lovejoy) is also brightest when it is closest to the Earth... ...At which time, the comet is also moving apparently fastest..
I managed to track this comet on 2015-01-04, but it was too faint for a spectrum in 5 minutes exposure

This could be an interesting project for when the Comet and the Moon (reference spectrum) are in the sky!.. But I might not have enough resolution for this, no? Do high-resolution spectra of comets show reflected features from solar spectrum (similar to gaseous planets)?